A 68-year-old right-handed woman with no history of brain damage or familial left-handedness was admitted to our hospital due to the acute onset of speech difficulty; her speech was nonfluent. Literal and phonological paraphasias, agrammatism and paragrammatism were observed. Brain MRI revealed an acute infarction in the right anterior cerebral artery territory, involving the right corpus callosum. Moreover, cerebral blood flow was decreased not only in the area of the right corpus callosum but also in the left fronto-temporal lobe, suggesting crossed diaschisis. This is a rare case of crossed aphasia following an infarction in the right corpus callosum.